The field of the invention relates to systems, methods and devices for detecting ionizing radiation. In particular, the present disclosure is directed to systems, methods and devices for efficient detection of ionizing radiation using measures of high energy and/or low energy charge carriers generated therefrom.
The need for detection and quantification of ionizing radiation, such as x-rays, γ photons and neutrons, is pervasive in many areas of technology, including national security, radiological response, and defense applications, as well as medical imaging, radiotherapy treatment, and radiation protection applications. The modern paradigm of radiation detection development has been to increase detector efficiency by improving the utilization of the incident ionizing radiation entering a detector volume, and enhanced signal processing. This has lead to increased sophistication of the hardware and software associated with the detectors, as well as in the energy conversion methods associated with the active regions of the detectors. For instance, in order to stop more particles and increase efficiency, many modern radiation detectors have required relatively large active volumes and mass, increasing cost and system bulk. In addition, such detectors generally implement high-voltage sources to collect or accelerate charge carriers, and require various signal amplification techniques. They are also susceptible to aging and tend to be sensitive to environmental conditions, such as temperature and humidity, including mechanical, thermal, and electrostatic shocks. In addition, because the active sensors in common radiation detectors can be up the order of a few inches in diameter and length, the solid angle, or, the angle viewed from the radiation source subtended by the detector area, is small. This means that it possible to detect only a fraction of the radiation emitted from the radiation source, adding a geometric constraint to the detector efficiency.
Previous technologies have utilized either indirect or quasi-direct methods for detecting ionizing radiation. Specifically, indirect methods convert incident ionizing radiation into electric signals by first depositing the energy of the ionizing radiation into the active bulk of a detector material, producing intermediate carriers of energy therein, which are then used in the formation of a measurable electric signal. In particular, the most common method includes use of a scintillator material, which when exposed to ionizing radiation absorbs and re-emits energy in the form of optical or ultraviolet (“UV”) photons. These photons are then detected using an optical or UV sensor and further amplified and processed to generate a usable electric signal.
On the other hand, the most common quasi-direct method for detecting ionizing radiation includes applying an external electric potential between two electrodes in a gas-filled chamber. Incident ionizing radiation generates ion pairs in the gas, which under the influence of the external electric potential are transported as positive and negative charges towards respective cathode and anodes, thus creating a measurable pulse or continuous current. In other quasi-direct methods, an electric pulse or continuous current is created from electron-hole pairs generated from the interaction of ionizing radiation with a bulk semiconducting material. The electron-hole pairs are then collected by externally charged electrodes.
Many present detector technologies are limiting and can demand large capital expenditure. Specifically, present day detector conversion of ionizing radiation via multiple mechanisms implies loss of efficiency, requiring higher complexity and detector bulk associated with increased cost of production and operation. For instance, in many field applications, such as portal monitoring, it is expensive to deploy, maintain and replace such detectors. In addition, limitations on detector capabilities can prevent miniaturization or decrease the power consumption. As an example, in hand-held devices, many detector types must be ruggedized to avoid damage, increasing their bulk and weight, thus limiting maneuverability and the agility of an operator in the field. In addition, owing to their specialized technology, such detectors cannot be easily modified and adapted to new conditions, including incorporation into new equipment or personal gear.
Given the above, there is a need for new systems and methods for detecting ionizing radiation. In particular, there is a need for detecting ionizing radiation in ways that are cost effective, allow scaling to large areas, are amenable to tight spaces, can conform to various geometrical shapes, and further need not rely on external power to generate measurable signals.